Recently, with the advancement of microcomputer technology and the rapid development of the electronic industry, a great variety of mobile devices have been developed and made commercially available, including personal digital assistants (PDAs), smart phones, and tablet PCs, to name only a few. These mobile devices typically are refined in structure, exquisite in appearance, and highly portable, and have therefore become one of the most popular products on the market. In order to reduce the space occupied by such a mobile device and make it possible to use such a device anytime anywhere, this kind of devices are usually as large as a user's hand or shaped as a panel the size of a notebook.
Now, thanks to the burgeoning touch control technology, touch screens are extensively used in mobile devices so that the conventional keyboards can be dispensed with to produce an even more polished look. Please refer to FIG. 1 for a mobile device 1 that is commonly seen nowadays. The mobile device 1 has a touch screen 10 and is operated as follows. Basically, a user can give all sorts of commands to the mobile device 1 (e.g., to execute a program, to adjust acoustic volume, etc.) by touching the touch screen 10 with a finger or a touch control input device (e.g., a stylus). When it is desired to input text into the mobile device 1, the mobile device 1 can be instructed to display a graphical keyboard 101 on the touch screen 10, wherein the graphical keyboard 101 is composed of a plurality of graphical keys 101a. By pressing any of such on-screen keys 101a, the touch screen 10 is triggered to send a corresponding command to the mobile device 1. The touch control operation described above not only is intuitive and user-friendly, but also eliminates the noise which may otherwise result from using a conventional keyboard to input text. Moreover, using the virtual keyboard 101 instead of a physical keyboard reduces the weight of the mobile device 1 significantly, which in turn increases convenience of use. However, such operation still has the following shortcomings:
(1) Difficulty in inputting commands accurately: As the mobile device 1 is generally designed to correspond in size to a pocket or a hand for enhanced portability, the area of the touch screen 10 is quite limited. It follows that the size of each graphical key 101a is also limited and seldom matches the size of a finger tip. Therefore, when the user presses a certain graphical key 101a, chances are the graphical keys 101a adjacent to the intended key are also pressed, thus leading to an incorrect or inaccurate input. Furthermore, unlike the conventional keyboards, the graphical keyboard 101 when pressed does not create a depressed feel to the user's finger, and absence of the such a depressed feel is very likely to be mistaken by the user as the mobile device 1's failure to sense the pressing action. As a result, the user tends to input the same command repeatedly and yet unnecessarily.
(2) Reduced display area on the touch screen: The fast development of network technology has made it commonplace for the mobile device 1 to have Internet connection functions, and it is often required to input text while using the mobile device 1 to browse webpages (e.g., to leave a message on a webpage, to input keywords in search for a specific website, etc.). During the webpage browsing process, however, the graphical keyboard 101 inevitably covers a significant portion of the display area on the touch screen 10 and thus causes inconvenience to the viewer.
As a solution to the aforesaid problems, the mobile device 1 can be additionally provided with a connector 11, as shown in FIG. 1, for connecting with an auxiliary keyboard 12 when it is desired to input text into the mobile device 1. The auxiliary keyboard 12, though capable of facilitating text input, compromises the portability of the mobile device 1. Besides, the auxiliary keyboard 12 must be placed on a flat surface (e.g., a tabletop) when used for input; in other words, the mobility of the mobile device 1 will be impaired. Therefore, the issue to be addressed by the present invention is to design an input device that can be used to input commands into a mobile device both accurately and conveniently.